The Department of Conservation have reported traces of the rat poison brodifacoum in the livers of two of five penguins recently found dead on Long Bay Beach.

However, DoC says this has been ruled out as the cause of death due to “low levels” saying penguin mortalities are not uncommon for this time of year.

Brodifacoum in 147 tonnes of cereal bait was aerially dropped on Rangitoto and Motutapu recently by DoC to eradicate mammal pests.

Marine educationalist Sarah Silverstar found six dead penguins on Waiheke beaches and has sent two to be tested for brodificoum. The results were due last Friday but the laboratory has sent the livers to Landcare Research for further testing. The results are now due tomorrow.

Ms Silverstar says according to studies toxicity rates and sensitivities differ between animals.

“It is important to remember that marine mammals are different to rats and there have been no studies on marine mammals or fish and the toxicity of brodificoum.

“In the 2003 study completed by the American College of Veterinary Pathologists dogs had been exposed to brodificoum four weeks before giving birth and seemed fine but gave birth to some dead puppies, some puppies that died within two days and others that survived. All contained traces of the poison.

“As demonstrated with these puppies, the lethal dose for one individual cannot affect another, and because all man-made chemicals operate at extremely low levels, ultimately the effects both long and short term are unknown.”

She cites a recent study by the pesticides programme manager of Hawaii Department of agriculture Robert Boesch.

“Brodificoum is a second generation anti-coagulant which was used on Hawaiian islands in February this year after the Environment Protection Agency removed the prohibition to drop it in or near water. Within a week dead fish and a juvenile whale were washed up on an adjacent island and the people who live on neighbouring islands can no longer eat the fish on which they depend and authorities have not told them what is going on.”

DoC said that tests on dolphin livers and stomach contents have come back negative for both brodifacoum and tetrodotoxin – the toxin found in sea slugs. They say tests on pilchards (taken from dead dolphins’ stomachs), mussels and pipis have also come back negative for brodifacoum.

They say they do not know the cause of the dolphin deaths and have asked the Cawthron Institute to test the dolphin samples for domoic acid – an algal toxin known to be a common cause of dolphin deaths. Results are expected this week. •

Minka Firth